A silicon photodiode is used in reverse bias to measure infrared light of wavelength 900 nm…

Step 1. The photon energy. $E = \dfrac{1240\ \text{eV nm}}{900\ \text{nm}} = 1.378$ eV, which is above the gap of $1.12$ eV, so every photon can make a pair.

Step 2. The responsivity. $\dfrac{I}{P} = \dfrac{\eta}{E} = \dfrac{0.80}{1.378\ \text{eV}} = 0.581\ \text{A/W}$.

Step 3. The photocurrent. $I = 0.581\ \text{A/W} \times 35 \times 10^{-6}\ \text{W} = 20.3\ \mu\text{A}$.

Step 4. The voltage. $V = IR = 20.3 \times 10^{-6}\ \text{A} \times 47 \times 10^{3}\ \Omega = 0.955$ V.